plate and large central ridge with pustule on central-basal portion of ridge and long, narrow outer posterior extension. Cutting edge of lateral tooth with large triangular major cusp, one inner flanking denticle and 2 or 3 outer flanking denticles. Marginal teeth is with wide shafts, narrow bases, and curved, hooked, blade-like apices bearing long pointed tips. Inner marginal tooth with 2 or 3 inner flanking denticles and 1 or 2 outer, flanking denticles; outer marginal tooth same, but lacking outer flanking denticles. 3. Morphology Differences With Other Species In the Same Genus The overall shape and sculpture of C. caeruleum are much like those seen in members of the genus Clypeomorus Jousseaume, and several authors have assigned this species to Clypeomorus, but the resemblance is superficial, as pointed out earlier in this monograph. Cerithium caeruleum is generally much larger than most Clypeomorus species. In size and overall morphology, it most closely resembles the sympatric species, Clypeomorus petrosa gennesi, which is also an intertidal, hard-substrate species. However, Cerithium caeruleum is larger, less pupiform, lacks the whorl sculpture of three tightly beaded spiral cords, and is distinctly more angulate in outline than Clypeomorus petrosa gennesi. There are also significant differences in the radulae of these two species. There is a remarkable convergence in shell morphology between Cerithium caeruleum and the batallariid, Batillaria sordidia family Potamididae. The overall color and shell sculpture of Cerithium caeruleum are very close to those observed in Batillaria sordida. Intraspecific morphological variation occurs in shell size and strength of sculpture. Due to the harsh intertidal environment, protoconchs are normally eroded, as is much of the shell sculpture. Some morphs are quite knobby while others may be smoother, especially on the body whorl. Immature specimens are fusiform with large, wide body whorls and resemble immature specimens of Cerithium echinatum Lamarck. Growth and Reproduction The egg capsules of C. caeruleum each have a diameter of 150 mm, and there is an incubation period of 4–5 days prior to hatching. Reproductive studies and growth statistics calculated by Ayal and Safriel provide evidence that this species lives from 90 to 120 days in the plankton and has a seven-year life history. Examination of the protoconch shows a sinusigeral notch and sculpture indicative of planktotrophy. Hulings (1986) found the sex ratio of males to females in a Gulf of Aqaba population to be 1:6. The major period of reproduction was from April through